Multimodal CT imaging of a posterior fossa stroke

Keywords Acute stroke Acute stroke imaging Acute stroke diagnosis Multimodal CT Perfusion-CTDear Editor,We describe a case of an 82-year-old woman with diabetesand hypertension who was admitted through our Emer-gency Department for a history of vertigo, nausea, vomit-ing, and left arm incoordination for 4 h. Neurologicalexamination revealed only left arm ataxia and strokewas suspected. National Institutes of Health Stroke Scale(NIHSS) score was 2. Multimodal stroke CT imaging wasobtained. CT of the brain was unremarkable. CT-angio-graphy (CTA) and near-whole brain perfusion CT (PCT)revealed occlusion of the left superior cerebellar artery(SCA) with corresponding compensated perfusion deficit inthe left cerebellar hemisphere, characterized by increasedmean transit time and increased cerebral blood volume(Fig. 1a–c), suggesting presence of viable ischemic pen-umbra. Considering the low NIHSS score with absence ofcompleted infarction on imaging, intravenous fluids andaspirin therapy were initiated. Follow-up MRI at 24 hdemonstrated only punctate infarcts in the left SCA terri-tory (Fig. 1d). Further work-up was negative for embolicsources. The patient rapidly recovered (NIHSS score 0) andwas discharged after 5 days on antiplatelet therapy.Advanced morphologic, vascular, and physiologic brainCT imaging has been established as a fast, reliable, andreadily available modality for stroke triage with the goal ofdistinguishing ischemic stroke from intracranial hemor-rhage and selecting patients likely to benefit from reper-fusion therapies [1, 2]. CT and MRI have comparableefficacy in the evaluation of supratentorial stroke; however,MRI is currently more sensitive and, therefore, the pre-ferred imaging modality for patients with posterior fossastroke [3]. One reason for the poor PCT sensitivity ofposterior fossa stroke is the limited anatomical coverageavailable on older CT scanners, generally limited to 2 or4 cm slabs of brain tissue typically centered at the level ofthe basal ganglia/lateral ventricles. Recent technologicaladvancements in multi-detector CT equipment haveexpanded the anatomical coverage of perfusion CT,thereby permitting routine assessment of the posterior fossawith a standard protocol [4]. This case report illustrates thediagnostic accuracy of such advanced multimodal CTimaging in acute posterior circulation ischemic strokepatients. In this particular case the imaging findings did notlead to change in treatment; however, they allowed for avery precise diagnosis and reassured the clinical manage-ment decisions.